The value of solar batteries as clean energy sources has been acknowledged, and the demands therefor are growing. Solar batteries can be used in a wide variety of fields, from power energy sources for large-scale devices to small-sized power sources for precision electronic devices. In order for solar batteries to be widely used in various fields, the properties of the batteries, especially the output characteristics thereof, need to be accurately measured. Otherwise, it is assumed that various problems may occur in the devices using the solar batteries. Therefore, a technology that can radiate high-precision artificial sunlight, which can be used for inspecting, measuring, and testing a solar battery, over a wide area is particularly in demand.
In recent years, artificial sunlight radiation devices are being developed as devices that can radiate artificial sunlight. Normally, such an artificial sunlight radiation device radiates artificial light (artificial sunlight) with uniform illuminance onto a light-receiving surface of a panel-shaped solar battery so as to be used for measuring, for example, the output characteristics of the solar battery.
The main element required in artificial sunlight is to make the emission spectrum thereof analogous to that of reference sunlight (established by Japanese Industrial Standard). However, in the artificial sunlight radiation device, since a light-source lamp is considered to be a spot or a line, it is extremely difficult to radiate light with uniform illuminance onto the entire light-receiving surface, which is planar, (or the entire area) of the solar battery. Patent Literature 1 discloses a technology in which the artificial sunlight radiation device is designed to adjust an illuminance variation therein.
Patent Literature 1 discloses an artificial sunlight radiation device in which halogen lamps and xenon lamps are installed in adjacent independent chambers. In detail, a dedicated optical filter is installed in an upper opening of each lamp, such that artificial sunlight is radiated onto the underside of the solar battery by turning on each lamp. Thus, by appropriately installing reflective plates inside the chambers in which the lamps are installed, an illuminance variation between the lamps can be adjusted.